Well, i wasn't specifically referring to them, the spacer and bolts they sell are kinda cool, my deal is Mixing the Pulleys AND brackets off my ol 66 273, to a 73 340 (converted to Steel Crank) I have No overheating issues, but that damn Alternator Alignment required me to mill a spacer down... But, Again, mismatched Year parts... from what I read. And the fact that the 66 to 73 was an AC engine... the three grooves are probably heavier than I need, ( I wanted to get to CVS set up, but I didn't jump on em when I Should have) but they Work Darn Good!